The RenderMan Interface - Paul Bourke

4.2.5 Displacement shading
The graphics state maintains a current displacement shader. Displacement shaders are procedures
that can be used to modify geometry before the lighting stage.
The RenderMan Interface includes one standard displacement shader: ”bumpy”. The definition
of this displacement shader is given in Appendix A, Standard RenderMan Interface
Shaders. The parameters controlling this displacement is given in Table 4.9.
RiDisplacement ( RtToken shadername, ...parameterlist...)
Set the current displacement shader to the named shader. shadername is the name of a
displacement shader.
If a particular implementation does not support the Displacements capability, displacement
shaders can only change the normal vectors to generate bump mapping,
and the surface geometry itself is not modified (see Displacement Shaders).
RIB BINDING
Displacement shadername ...parameterlist...
EXAMPLE
RiDisplacement (”displaceit”, RI NULL);
SEE ALSO
RiDeformation, RiMakeBump, RiSurface
Surface Name Parameter Type Default Description
bumpy amplitude float 1.0 Bump scaling factor
texturename string ”” Displacement map name
Table 4.9: Standard Displacement Shader Parameters
4.2.6 Volume shading
The graphics state contains a current interior volume shader, a current exterior volume shader,
and a current atmosphere shader. These shaders are used to modify the colors of rays traveling
through volumes in space.
The interior and exterior shaders define the material properties on the interior and exterior
volumes adjacent to the surface of a geometric primitive. The exterior volume relative
to a surface is the region into which the natural surface normal points; the interior is the
opposite side. Interior and exterior shaders are applied to rays spawned by trace() calls in
a surface shader. Renderers that do not support the optional Ray Tracing capability will
also not support interior and exterior shaders.
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